FROM THE FARM REPORT: RUMINATION TIME MATTERS MORE THAN YOU THINK

Rumination is a fundamental cow behavior with wide-ranging implications for digestion, health, and productivity. Rechewing feed increases saliva flow, helps maintain rumen pH, and supports fiber degradation. When rumination declines, feed intake and rumen health often suffer soon after. Because rumination responds quickly to changes in a cow’s status, it often declines before milk yield drops or visible signs of illness appear. That is why rumination has become a valuable management tool on dairies today.

At Miner Institute we’ve been monitoring rumination in our lactating herd since 2012 using a collar- based system. We rely on this information to detect cows in heat, identify sick cows earlier, manage transition challenges, and evaluate the effectiveness of our heat-stress control strategies. Like many farms, we initially viewed rumination primarily as a short-term alert system. New research suggests it may be much more than that.

A recent study published in the Journal of Dairy Science (https://doi.org/10.3168/jds.2025-27826) makes a strong case that rumination time, especially around first calving, reflects a cow’s underlying resilience and long-term performance. The researchers followed more than 3,500 Holstein heifers using accelerometer-based collars from 60 days before to 60 days after calving. They found that cows with higher rumination times tended to produce more milk, return to breeding sooner, and experience fewer health problems.

The first transition into lactation is a major test for heifers. Nutrient demands increase rapidly, housing and social environments change, and management routines shift. Not all heifers respond to these stressors in the same way. This difference is especially apparent in rumination patterns around calving. Some heifers show a sharp decline in rumination, while others maintain a steadier pattern. The magnitude of the drop reflects how strongly a cow responds to stress, and the speed of recovery reflects how quickly she returns to normal function. In other words, rumination provides a window into resilience.

One of the most interesting findings from the study is that rumination time is heritable, with estimates ranging from 0.06 to 0.62, depending on timing. The highest heritability occurred during the last month before calving. This suggests that cows differ consistently in their ability to maintain rumination when challenged. In contrast, rumination time during the first 2 weeks after calving showed low heritability, likely because environmental and management factors play a larger role immediately after calving.

This research helped put words and numbers to something we have noticed at our farm for years. Even when cows are fed the same diet and managed similarly, rumination times vary among individual cows. Some cows are simply better ruminators than others. The new findings suggest that these differences are not random and may reflect inherent biological traits rather than just day-to-day management effects.

The researchers also asked an important practical question: can rumination time be used not only for daily cow management but also as a trait for genetic improvement, especially in first-calving heifers? From a management standpoint, this means we should look beyond single alerts and focus on trends over time, compare cows at the same stage of lactation, and pay close attention to heifers with consistently low rumination before and after calving.

Ultimately, this study reinforces that rumination is not just a short-term signal. It reflects a cow’s biology and her ability to cope with stress. Because rumination is heritable and favorably associated with milk production, fertility, and health, it may play a role in future breeding goals aimed at improving resilience. This research supports what many farmers and our herdsmen at Miner already know: cows that chew well do well.

— Heather Dann

dann@whminer.com